Gale Warning 578, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AKDT SAT SEP 12 2009

.ANALYSIS AND UPPER LEVELS...
UPPER LEVEL PATTERN THIS MORNING HAS A BROAD LONGWAVE TROUGH SITUATED
OVER THE NORTHWEST COAST AND EXTENDING DOWN INTO THE BERING SEA.  A
CLOSED UPPER LEVEL LOW IN THE BASE OF THIS TROUGH STACKS WELL WITH A
SURFACE LOW IN THE BERING.  IN THE EAST A SHORTWAVE TROUGH LINGERS
OVER THE GULF COAST BUT OVERALL THE FLOW IS MAINLY SOUTHWESTERLY
ACROSS THE MAINLAND.  AT THE SURFACE THE MOST SIGNIFICANT FEATURE IS
THE LOW PRESSURE CENTER IN THE BERING SEA...WITH A WEAK LOW JUST
SOUTH OF THE PRINCE WILLIAM SOUND THIS MORNING.  OVER THE NEXT COUPLE
OF DAYS THE LONGWAVE TROUGH IS EXPECTED TO SHIFT EASTWARD...WITH A
LONGWAVE RIDGE BUILDING IN BEHIND IT OVER THE WESTERN ALEUTIANS.
THIS BRINGS A NORTHERLY JET TO THE CENTRAL ALEUTIANS AGAIN WITH A
BROAD AREA OF INSTABILITY OVER MAINLAND ALASKA.

.MODEL DISCUSSION...
MODELS WERE IN GOOD AGREEMENT AGAIN TONIGHT THROUGH THE MID RANGE.
GFS WAS THE MODEL OF CHOICE...ALTHOUGH FEW EDITS WERE MADE TO THE
CURRENT FORECAST.  LONGER RANGE...MODELS MATCHED UP WELL IN THE WEST
BUT WERE STILL UNDECIDED ON THE STRENGTH AND TRACK OF THE LOW
FORECAST TO MOVE INTO THE GULF NEXT WEDS/THURS.  WITH LACK OF
CONFIDENCE IN THE NEW SOLUTIONS IT WAS DECIDED TO STICK WITH THE
PREVIOUS FORECAST.

.SHORT TERM FORECAST...
IN THE EAST...THE LOW IN THE GULF OF AK IS STILL HANGING ON ALTHOUGH
IT CONTINUES TO WEAKEN.  WINDS HAVE SIGNIFICANTLY DECREASED ACROSS
THE AREA AND ALTHOUGH SOME GUSTY WINDS MAY OCCUR ALONG THE NORTH GULF
COAST WITH THE BARRIER JET THEY ARE NOT EXPECTED TO REACH GALE FORCE.
 MAIN WEATHER FOR THE WEEKEND WILL BE SHOWERS ACROSS THE AREA AS THE
UPPER LEVEL INSTABILITY LINGERS. MOST OF THE PRECIPITATION WILL
REMAIN ALONG THE GULF COAST...ALTHOUGH SOME SHOWERS ARE EXPECTED TO
SNEAK ACROSS THE COASTAL MOUNTAINS INTO THE COPPER RIVER BASIN AND
THE ANCHORAGE BOWL IN PARTICULAR.  LEE SIDE AREAS IN PARTICULAR MAY
SEE PATCHY FOG DURING NIGHTTIME HOURS AS SOME BREAKS IN THE CLOUDS
MOVE OVERHEAD.

OUT WEST...RAIN FROM THE LOW IN THE BERING IS ALREADY MOVING ONSHORE
THIS MORNING ALONG THE WEST COAST AND IS EXPECTED TO CONTINUE
THROUGHOUT THE DAY.  FURTHER INLAND AREAS SUCH AS THE NORTHERN
BRISTOL BAY REGION INTO THE KUSKOKWIM VALLEY WILL SEE MORE SHOWERY
TYPE PRECIPITATION.  AS THE LOW MOVES OVER THE AK PEN AND INTO THE
GULF OF AK TODAY AND TOMORROW PRECIP WILL CONTINUE...BUT WINDS ARE
NOT EXPECTED TO PICK UP UNTIL SUNDAY NIGHT WHEN THE NORTHERLY JET
MOVES OVERHEAD ALONG THE ALASKA PENINSULA.  IN SPITE OF THE NORTHERLY
JET THESE WINDS WILL NOT BE EXTREMELY STRONG AND ARE NOT EXPECTED TO
REACH GALE FORCE.

BERING SEA/ALEUTIANS...WINDS WILL BE A LITTLE STRONGER FOR THE
ALEUTIAN CHAIN THROUGH THE WEEKEND AS THE LONGWAVE RIDGE STRENGTHENS
OVER THE WESTERN ALEUTIANS BEHIND THE LOW.  GALE FORCE WINDS CAN BE
EXPECTED WITH THAT TIGHTENED GRADIENT BRINGING NORTHERLY FLOW TO THE
CENTRAL ALEUTIANS THROUGH TUESDAY.  OTHERWISE...WEATHER SHOULD BE
FAIRLY CALM AS THE RIDGE MOVES OVERHEAD. AS ALWAYS LOW STRATUS AND
FOG IS TO BE EXPECTED WITH HIGH PRESSURE MOVING IN.

.LONG TERM FORECAST...
THE EARLY PART OF NEXT WEEK LOOKS TO BRING IMPROVING WEATHER FOR THE
MAINLAND BUT WORSENING WEATHER FOR THE WESTERN ALEUTIANS.  AS THE LOW
IN THE BERING TRANSITIONS TO A GULF OF AK LOW A WEAK RIDGE WILL BUILD
IN FROM THE EAST OVER THE MAINLAND...WHICH WILL BRING CLEARING SKIES.
IN THE WESTERN ALEUTIANS HOWEVER A NEW LOW PRESSURE SYSTEM WILL MOVE
IN FROM THE SOUTHWEST.  THE STRENGTH OF THIS LOW IS STILL IN QUESTION
BUT WINDS WILL BE GALE FORCE AT LEAST.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 170 172 176 179
FIRE WEATHER...NONE

LEWF SEP 09